Dose-dependent effects of tetraethylammonium on circling spreading depressions in chicken retina.
The K+-channel blocker tetraethylammonium (TEA) was applied to study its effects in self-sustaining, circling spreading depression in the chicken retina (RSD). Extracellular K+ (Ke+ activities and the direct-current (DC) signal were recorded using double-barrelled microelectrodes. Superfusion of TEA-concentrations of 10 to 250 microM for 4 to 7 min reduced the RSD-associated DC amplitude (by 9 to 45%) and the maximum of the K+ concentration (by 9 to 34%) in a dose-dependent manner. Propagation velocity of the RSD was lowered by 24%. At concentrations higher than 250 microM TEA (0.5 to 10 mM), the propagation was slowed by more than 60%, after which the RSD disappeared. Recovery upon reperfusion with Ringer was immediate. These observations illustrate: 1) TEA affects the Ke+ changes during RSD at very low concentrations. 2) The reduced Ke+ transients are accompanied by a reduction of the DC shifts. 3) These changes of the electrical properties of the RSDs are paralleled by a reduction of the propagation velocity. 4) The effects of TEA are reversible. 5) The changes of these parameters occur dose-dependently. These data suggest a close relationship between the amplitudes of the ionic/electric changes during RSDs and the mechanisms of propagation.
Scheller
D
D
Janssen Research Foundation, Neuss, Germany.
Tegtmeier
F
F
Schlue
W R
WR
D000818:Animals; D002645:Chickens; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D008839:Microelectrodes; D015221:Potassium Channels / Q000187:drug effects*; D012160:Retina / Q000187:drug effects*; D019789:Tetraethylammonium / Q000494:pharmacology*
D015221:Potassium Channels; D019789:Tetraethylammonium